The Soviet invasion of Manchuria or, as the
Soviets named it, the Manchurian Strategic Offensive
Operation (Russian: Манчжурская стратегическая наступательная
операция, lit. Manchzurkaya Strategicheskaya Nastupatelnaya
Operaciya), began on August 9, 1945, with the Soviet invasion of
the Japanese puppet
state of Manchukuo
and was the largest campaign of the 1945 Soviet-Japanese War.
The Soviets conquered Manchukuo, Mengjiang (inner Mongolia), northern Korea, southern Sakhalin, and the Kuril Islands. The rapid defeat of
Japan's Kwantung
Army was a significant factor in the Japanese surrender and the
termination of World War II.

The commencement of the invasion fell between the atomic bombings of Hiroshima, on August 6,
and Nagasaki, on August 9. Although Soviet
leader Joseph
Stalin had not been told much detail of the Western Allies'
atomic bomb
program by Allied governments, he was nonetheless well aware of
its existence and purpose by means of Soviet intelligence sources.
However, by virtue of the timing of the agreements at Tehran and
Yalta, and the long term buildup of Soviet forces in the Far East
since Tehran, it is clear that news of the attacks on the two
cities played no major role in the timing of the Soviet invasion;
the date of the invasion was foreshadowed by the Yalta agreement,
the date of the German surrender, and the fact that on August 3, Marshal
Vasilevsky reported to Stalin that, if necessary, he could
attack on the morning of August 5.

At 11pm Trans-Baikal time on 8 August 1945, Soviet foreign
minister Molotov informed Japanese ambassador
Sato that the
Soviet Union had
declared war on the Empire of Japan, and that from August 9
the Soviet Government would consider itself to be at war with
Japan.[5]
At one minute past midnight Trans-Baikal time on 9 August 1945, the
Soviets commenced their invasion simultaneously on three fronts to
the east, west and north of Manchuria. The operation was subdivided
into smaller operational and tactical parts:

Though the battle extended beyond the borders traditionally
known as Manchuria—that is, the traditional lands of the
Manchus—the coordinated and integrated
invasions of Japan's northern territories has also been called
the Battle of Manchuria.[6]
Since 1983, the operation has sometimes been called
Operation August Storm, after American Army
historian LTC David
Glantz used this title for a paper on the subject.[1]
It has also been referred to as the battle of Manchukuo,
the Soviet invasion of Manchuria., and by its Soviet name,
the Manchurian Strategic Offensive Operation.

However, with success at Stalingrad, the Soviet attitude to
Japan changed, both publicly, with Stalin making speeches
denouncing Japan, and "privately", with the Soviets building up
forces and supplies in the Far East. At the Tehran
Conference (November 1943), amongst other things, Churchill,
Roosevelt and Stalin agreed that the Soviet Union would enter the
war against Japan once Nazi Germany was defeated. The Soviet
buildup in the Far East continued, and by early 1945 it had become
apparent to the Japanese that the Soviets were preparing to invade
Manchuria; in addition to their problems in the Pacific, the
Japanese realised they needed to determine when and where such an
invasion would occur.

At the Yalta Conference (February 1945),
amongst other things, Stalin secured from Roosevelt the promise of
Stalin's Far Eastern territorial desires, in return agreeing to
enter the Pacific war within two or three months of the defeat of
Germany. By the middle of March 1945, things were not going well in
the Pacific for the Japanese, and they withdrew their elite troops
from Manchuria to support actions in the Pacific. Meanwhile the
Soviets continued their Far Eastern buildup. The Soviets had
decided that they did not wish to renew the Neutrality Pact. The
terms of the Neutrality Pact required that 12 months before its
expiry, the Soviets must advise the Japanese of this, so on 5 April
1945 they informed the Japanese that they did not wish to renew the
treaty.[9]
This caused the Japanese considerable concern,[10][11] but
the Soviets went to great efforts to assure the Japanese that the
treaty would still be in force for another twelve months, and that
the Japanese had nothing to worry about.[12]

On 9 May 1945 (Moscow time), Germany surrendered, meaning that
if the Soviets were to honour the Yalta agreement, they would need
to enter war with Japan by 9 August 1945. The situation continued
to deteriorate for the Japanese, and they were now the only axis
power left in the war. They were keen to keep at peace with the
Soviets and extend the Neutrality Pact,[12]
and they were also keen to achieve an end to the war. Continuously
since Yalta they had repeatedly approached, or tried to approach,
the Soviets in order to extend the neutrality pact, and to enlist
the Soviets in negotiating peace with the allies. The Soviets did
nothing to discourage these Japanese hopes, and drew the process
out as long as possible (whilst continuing to prepare their
invasion forces.)[12]
One of the roles of the Cabinet of Admiral Baron Suzuki, which took
office in April 1945, was to try to secure any peace terms short of
unconditional surrender.[13]
In late June they approached the Soviets, (the Neutrality Pact was
still in place), inviting them to negotiate peace with the allies
in support of Japan, providing them with specific proposals and in
return they offered the Soviets very attractive territorial
concessions. Stalin expressed interest, and the Japanese awaited
the Soviet response. The Soviets continued to avoid providing a
response. The Potsdam Conference was held from 16
July to 2 August 1945. On 24 July the Soviet Union recalled all
embassy staff and families from Japan. On 26 July the conference
produced the Potsdam Declaration whereby
Churchill, Truman and Chiang Kai-shek (the Soviet Union was not at
war with Japan) demanded the unconditional surrender of Japan. The
Japanese continued to wait for the Soviet response, and avoided
responding to the declaration.[12]

The Japanese had been monitoring Trans-Siberian Railway traffic
and Soviet activity to the east of Manchuria and in conjunction
with the Soviet delaying tactics, this suggested to them that the
Soviets would not be ready to invade east Manchuria before the end
of August. They did not, however, have any real idea, and no
confirming evidence, as to when or where any invasion would
occur.[14]

The Japanese were caught completely by surprise when the Soviets
declared war an hour before midnight on 8 August 1945, and invaded
simultaneously on three fronts just after midnight on 9 August.

As a secondary objective, the 1st Far East Front was to prevent
Japanese forces from escaping to Korea, and then invade the Korean peninsula up to the 38th
parallel[1],
establishing in the process what later became North Korea. The
secondary objective was to be carried out by the 25th Army.[1]
Meanwhile, the 35th Army was tasked with capturing the cities of Boli (or Poli), Linkou and Mishan.[1]

Each Front had "front units" attached
directly to the Front instead of an army.[1]
The forces totaled 89 divisions with 1.5 million men,
3,704 tanks, 1,852 self propelled guns, 85,819 vehicles and
3,721 aircraft. Approximately one-third of its strength was in
combat support and services.[1]
Its naval forces contained 12 major surface combatants, 78
submarines, numerous amphibious craft, and the Amur
riverflotilla, consisting of gunboats
and numerous small craft. The Soviet plan incorporated all the
experience in maneuver warfare that the Soviets had acquired
fighting the Germans.[1]

Each Area Army (Homen Gun, the equivalent of a Western "army") had
headquarters units and units attached directly to the Area Army, in
addition to the field armies (the equivalent of a Western corps).
In addition to the Japanese, there was the forty thousand strong Manchukuo Defense Force,
composed of eight under-strength, poorly-equipped, poorly-trained
Manchukuoan divisions. Korea,
the next target for the Soviet Far East Command, was garrisoned by
the Japanese Seventeenth Area
Army.

The Kwantung Army had over six hundred thousand men in
twenty-five divisions (including two tank divisions) and six
Independent Mixed Brigades.
These contained over 1,215 armored vehicles (mostly armored cars
and light tanks), 6,700 artillery pieces (mostly light), and 1,800
aircraft (mostly trainers and obsolete types; they only had 50
first line aircraft). The Imperial Japanese Navy
contributed nothing to the defense of Manchuria, the occupation of
which it had always opposed on strategic grounds.

On economic grounds, Manchuria was worth defending since it had
the bulk of usable industry and raw materials outside of Japan and
was still under Japanese control in 1945. However, the Japanese
forces (Kwantung Army) were far below authorized strength; most of
their heavy military equipment and all of their best military units
had been transferred to the Pacific front over the previous three
years. By 1945, the Kwantung Army contained a large number of raw
recruits. As a result, the Kwantung Army had essentially been
reduced to a light infantry counter-insurgency force with limited
mobility and experience. On paper, the Japanese forces were no
match for the highly mobile mechanized Red Army, with its vastly superior tanks,
artillery, experience and tactics.

Compounding the problem, the Japanese military made many wrong
assumptions and major mistakes, the two most significant being:

They wrongly assumed that any attack coming from the west would
follow either the old railroad line to Hailar, or head in to Solun from the eastern tip of
Mongolia. The Soviets did attack along those routes, but their main
attack from the west went through the supposedly impassable Greater Khingan
range south of Solun and into the center of Manchuria.

Japanese military intelligence failed to
determine the nature, location and scale of the Soviet buildup in
the Far East. Based on initial underestimates of Soviet strength,
and the monitoring of Soviet traffic on the Trans-Siberian railway,
they believed the Soviets would not have sufficient forces in place
before the end of August, and that an attack was most likely in
Autumn 1945 or in the Spring of 1946.

Due to the withdrawal of the Kwantung Army's elite forces for
redeployment into the Pacific Theatre, new operational plans for
the defence of Manchuria against a seemingly inevitable Soviet
attack were made by the Japanese in the Summer of 1945. These
called for the redeployment of the majority of forces from the
border areas; the borders were to be held lightly and delaying
actions fought while the main force was to hold the southeastern
corner in strength (so defending Korea from attack).[15]

Further, they had only observed Soviet activity on the
Trans-Siberian railway and along the east Manchurian front, and so
were preparing for an invasion from the east. They believed that
when an attack occurred from the west, the redeployed forces would
be able to deal with it.[14][15]

However, although this redeployment had been initiated, it was
not due to be completed until September, and hence the Kwantung
Army were in the middle of redeployment when the Soviets launched
their attack simultaneously on all three fronts.

Campaign

Japanese soldier surrendering to Soviet soldiers.

The operation was carried out as a classic double pincer movement
over an area the size of Western Europe. In the western pincer,
the Red Army advanced over
the deserts and mountains from Mongolia, far from their resupply railways.
This confounded the Japanese military analysis of Soviet logistics,
and the defenders were caught by surprise in unfortified positions.
The Kwantung Army commanders were involved in a planning exercise
in (where) at the time of the invasion, and were away from their
forces for the first eighteen hours of conflict. Communication
infrastructure was poor, and communication was lost with forward
units very early on. However, the Kwantung Army had a formidable
reputation as fierce and relentless fighters, and even though
understrength and unprepared, put up strong resistance at the town
of Hailar which tied down some
of the Soviet forces. At the same time, Soviet airborne units were
used to seize airfields and city centers in advance of the land
forces, and to ferry fuel to those units that had outrun their
supply lines. The Soviet pincer from the east crossed the Ussuri and
advanced around Khanka
Lake and attacked towards Suifenhe, and although Japanese defenders
fought hard and provided strong resistance, the Soviets proved
overwhelming. Perhaps the most glaring fact illustrating the
differences in efficacy between the two opponents was that, often,
the speed of Soviet advances far outpaced any sort of fighting
withdrawal the Japanese could conduct, which formed a crucial
element of the entire Japanese strategy for defending the
Manchurian heartland.

After a week of fighting, during which Soviet forces had
penetrated deep into Manchukuo, Japan's Emperor Hirohito recorded the Gyokuon-hōsō which was broadcast on radio
to the Japanese nation on August 15, 1945. The idea of surrender
was incomprehensible to the Japanese people, and combined with
Hirohito's use of formal and archaic language, the fact that he did
not use the actual word "surrender", the poor quality of the
broadcast, and poor lines of communication, there was some
confusion amongst the Japanese about what the announcement actually
meant. The Imperial Japanese Army Headquarters did not immediately
communicate the cease-fire order to the Kwantung Army, and many
elements of the army either did not understand it, or ignored it.
Hence, pockets of fierce resistance from the Kwantung Army
continued, and the Soviets continued their advance, largely
avoiding the pockets of resistance, reaching Mukden, Changchun and Qiqihar by August 20. On the Soviet right
flank, the Soviet-Mongolian
Cavalry-Mechanized Group had entered Inner Mongolia and quickly took Dolon Nur and Kalgan. The Emperor of
Manchukuo (and former Emperor of China), Puyi, was captured by the Soviet Red Army. The
cease-fire order was eventually communicated to the Kwantung Army,
but not before the Soviets had made most of their territorial
gains.

On August 18, several Soviet amphibious landings had been
conducted ahead of the land advance: three in northern Korea, one
in Sakhalin, and one in
the Kuril
Islands. This meant that, in Korea at least, there were already
Soviet soldiers waiting for the troops coming overland. In Sakhalin
and the Kurils, it meant a sudden and undeniable establishment of
Soviet sovereignty.

The land advance was stopped a good distance short of the Yalu River, the beginning
of the Korean peninsula, when even the aerial
supply lines became unavailable. The forces already in Korea were
able to establish a bit of control in the peninsula's north, but
the ambition to take the entire peninsula was cut short when
American forces landed at Incheon on September 8, six days after the
signing of the Japanese Instrument of
Surrender.

Importance and
consequences

The Manchurian Strategic Offensive Operation, along with the two
atomic bombings of Hiroshima and Nagasaki,
combined to break the Japanese political deadlock and force Japan's
surrender; they made it clear that Japan had no hope of holding
out, even in the Home
Islands.

In the "Sixty years after Hiroshima" issue of the Weekly
Standard, American historian Richard B. Frank points out that there
are a number of schools of thought with varying opinions of what
caused the Japanese to surrender. He describes what he calls the
"traditionalist" view, which asserts that the Japanese surrendered
because the Americans dropped the atomic bombs. He goes on to
summarise other points of view.[16]

Tsuyoshi
Hasegawa's research has led him to conclude that the atomic
bombings were not the principal reason for Japan's capitulation. He
argues it was the swift and devastating Soviet victories on the
mainland in the week following Joseph Stalin's August 8 declaration of
war that forced the Japanese message of surrender on August 15,
1945.[17]
Others with similar views include The "Battlefield" series
documentary,[2]
Drea,[14]
Hayashi,[15]
and numerous others, though all, including Hasegawa, state that the
surrender was not due to any single factor.

The Soviet invasion and occupation of the defunct "Manchukuo"
marked the start of a traumatic period for the
more-than-one-million "Japanese" occupants of the puppet state. The
"native" Manchurians wanted to be rid of these "foreigners" - many
of whom were born in "Manchukuo" and had never been to Japan. Many
were killed, many others ended up in Siberian prisons for up to 20
years, and some made their way to the Japanese home islands, where
they were also treated as "foreigners".[13][18][19][20]

Manchuria was "cleansed" by Soviet forces of any potential
military resistance. With Soviet support for the spread of
Communism,[21]
Manchuria provided the main base of operations for Mao Zedong's forces, who
proved victorious in the following four years of the Chinese Civil
War, despite Soviet delays in withdrawing forces in order to
allow Chiang Kai-Shek's forces to redeploy to Manchuria first.
These military success in Manchuria and China by the Communist
Chinese led to the Soviet Union giving up their rights to bases in
China — promised by the Western Allies — because all of what the
Soviets considered Chinese land conquered in the invasion (as
distinct from Soviet land liberated from the Japanese) was
eventually turned over to the People's Republic of China.[21]
Note, however, that before leaving Manchuria, Soviet forces and
bureaucracy dismantled almost all of the portable parts of the
considerable Japanese built industry in Manchuria and relocated it
to "restore industry in war-torn Soviet territory". That which was
not portable was either disabled or destroyed; the Soviets had no
desire for Manchuria to be an economic rival, particularly to the
underdeveloped Far Eastern Soviet Territories.[13]

As agreed at Yalta, the Soviet Union had intervened
in the war with Japan within three months of the German surrender,
and they were therefore entitled to the territories of Sakhalin and
the Kuril Islands and also to preeminent interests over Port
Arthur and Dalian, with
its strategic rail connections. The territories on the Asian
mainland were subsequently transferred to the full control of the
People's Republic of China in 1955; the other possessions are still
administered by the Soviet Union's successor state,
Russia.

Though the north of the Korean peninsula
was under Soviet control, the logistic machine driving the invasion
forces had given out before the entire peninsula could be seized.
With the American landing at Incheon — some time before the Red
Army could have remobilized and secured the entire peninsula — Korea was
effectively divided. This was a precursor to the Korean War five years
later.